MODEL PENDUGAAN KANDUNGAN AIR, LEMAK DAN ASAM LEMAK BEBAS PADA TIGA PROVENAN BIJI JARAK PAGAR (Jatropha curcas L.) MENGGUNAKAN SPEKTROSKOPI INFRAMERAH DEKAT DENGAN METODE PARTIAL LEAST SQUARE (PLS) - LENGKEY, LADY C. E. CH.; BUDIASTRA, I WAYAN; SEMINAR, KUDANG B.; PURWOKO, BAMBANG S. (Pusat Penelitian dan Pengembangan Perkebunan)
ABSTRAKJarak pagar berpotensi sebagai sumber biodiesel karena kandunganlemak yang tinggi (>40%) dan belum ada penggunaan lainnya.Spektroskopi (Near Infrared) NIR adalah metode yang cepat untukmengukur spektrum sampel dan tidak terdapat limbah kimia. Tujuanpenelitian adalah mengembangkan metode pendugaan komposisi kimiabeberapaÂ provenanÂ jarakÂ pagarÂ berdasarkanÂ spektroskopiÂ NIRmenggunakan kalibrasi PLS. Pengujian dilakukan menggunakan tigaprovenan jarak pagar yaitu IP-3A, IP-3M, dan IP-3P masing-masing 85sampel. Spektrum reflektansi diukur menggunakan alat NIRFlex SolidsPetri pada panjang gelombang 1000â2500 nm. Sekitar â jumlah sampeldigunakan untuk mengembangkan persamaan kalibrasi dan â jumlahsampel untuk validasi. Pra perlakuan data spektrum dilakukan dengannormalisasi antara 0-1, turunan pertama Savitzky-Golay 9 titik dangabungan keduanya. Hasil penelitian menunjukkan spektroskopi NIRdapat menduga kadar air, lemak, dan asam lemak bebas . Koefisienkorelasi (r) antara komponen kimia metode acuan dengan dugaan NIR>0,83 menunjukkan ketepatan model cukup baik (r kadar air=0,96, r kadarlemak=0,92, dan r ALB=0,89 ). Konsistensi model kalibrasi kadarair=94,85%, lemak=82,56%, dan ALB=87,80%. Koefisien keragamandugaan (Prediction Coeficient Variability/PCV) ketiga model <10%menunjukkan model yang dibangun cukup handal. Ratio of standard errorprediction to deviation (RPD) menunjukkan metode spektroskopi NIRdapat digunakan untuk menentukan kadar air (RPD=3,30) dan lemak(RPD=2,06). Model-model yang dikembangkan secara umum layakuntuk menentukan kadar air dan lemak biji jarak pagar, tetapi belumoptimal untuk penentuan kadar ALB biji jarak pagar.Kata kunci: NIR , jarak pagar, kadar air, kadar lemak, kadar asam lemakbebasABSTRACTPhysic nut is a potential source of biodiesel. It is high in fat content,above 40% and has not been usesed for other purposes. Moisture, free fattyacid, and fat content are the chemical compounds and determinant factorfor physic nut seed quality. The objective of this study was to develop amethod to predict chemical composition of physic nut by NIRspectroscopy and PLS calibration. The study was conducted using threeprovenances of physic nut, i.e. IP-3A, IP-3M, and IP-3P, with 85 sampleseach. The wavelengths of near infrared reflectance ranged from 1000 to2500 nm, and measured by NIR Flex Solids Petri Apparatus.Approximately â of total samples were used for developing calibrationequation, while â of total samples for performing validation. Pre-treatmentof spectrum data was done by applying normalization, first derivative ofSavitzkyâGolay 9 points, and as well as their combination. The resultsshowed that NIR spectroscopy performed acceptable prediction formoisture and fat content. Correlation coefficients (r) between the referencemethod and NIR prediction were 0.96 for moisture content, 0.92 for fatcontent, and 0.89 for FFA and the consistency of the model were 94.85%for moisture content, 82.56% for fat, and 87.80% for FFA. Prediction ofcoefficient of variability (PCV) of the three models â¤10 % shows that themodels are reliable. Ratio of standard error prediction to deviation (RPD)for moisture content has the potential to be used for screening (RPD=3.30)though the fat content model has rough screening (RPD=2.06).Key words: NIR, physic nut, moisture, fat, free fatty acid contents.